Answer:
A) The role of bacteria fixing nitrogen is very important because it fixes atmospheric nitrogen in the roots of plants. For example, Azotobacter is a bacteria which lives in the root of the higher plants. The bacteria fixes nitrogen for the plant and the plant gives habitat and food to the bacteria and hence, both get benefit.
B) Nitrifying bacteria are the bacteria which converts ammonia into nitrates. Examples are Nitrosomonas and Nitrobacter.
C) Denitrifying bacteria is a type of bacteria which converts nitrates into atmospheric nitrogen. Examples are Serratia and Pseudomonas.
